The Massachusetts General Hospital has a longstanding tradition of excellence in clinical and basic investigations in Reproductive Endocrinology. This tradition remains quite alive to date and is currently embodied by a group of actively-collaborating investigators whose research in reproduction covers a spectrum from basic molecular biology to clinical investigation. Four individual Units (Reproductive Endocrine, General Endocrine, Thyroid, and Developmental Biology) represent the center of these activities. Each has developed a critical mass of staff and an increasing network of informal collaborations over the past decade that capitalizes upon their individual strengths. In recognition of this growing interdependence, we propose to formalize these interactions with the establishment of a Reproductive Endocrine Sciences Center via the P30 Center mechanism consisting of 6 Core facilities: Administrative, Molecular Biology, Peptide Synthesis/Protein Sequencing, Histology/Organ Culture, Cell Culture, and Radioimmunoassay. The Cores will serve 15 investigators with 20 grants from 4 separate departments. This Center structure will dramatically widen the scope of scientific interactions among the center investigators and should translate to unusually swift transfer of basic advances into the clinical arena in this setting. The investigators responsible for the Core facilities are each mid-career scientists with considerable institutional stability; are recognized leaders in the areas of their proposed Core responsibilities; employ state-of-the-art technologies; and provide the Center both competent supervision and considerable economies of scale and improved cost effectiveness. The institutional setting for this proposal is unique in its traditions of commitment to basic and clinical biomedical-investigations, its current composition of productive investigators, and its commitment to the present proposal. The proposed Reproductive Endocrine Sciences Center therefore offers the proper constellation of excellence, efficiency, and collaborative science to result in a marked augmentation in research in Reproductive Endocrinology in this setting, given support by the establishment of a P30 Center.